This invention relates to optical communication systems and, more particularly, to a method of and apparatus for enabling the remote optical powering of an optoelectronic switch.
A network of desktop computers can be connected with Gigabit Ethernet transmitted over multimode optical fibers. As shown in FIG. 1, using the present standard approach, each computer 100 has a network interface card (NIC) 101 with an optical transceiver 102 (laser transmitter and optical receiver) connected over a pair of optical fibers 103 to a central switch or hub unit 104. Since a number of computers (typically 12 or more) can be connected to the switch unit 104, a corresponding number of optical transceivers 105 is needed to interface to the optical fibers 103. These transceivers 105 represent a significant portion of the cost and bulk of the switch unit 104 and act as a limitation on the number of optical input/output data (I/O) networks which can be supported by the switch unit 104.
Optoelectronic devices with integrated silicon electronics accommodate large numbers of optical inputs and outputs and offer potential size and cost reductions for optical data network applications. In particular, optoelectronic chips with over 4000 optical modulators and detectors have been demonstrated. Optoelectronic integrated circuit chips with vertical cavity surface emitting lasers (VCSELs) have recently been described in reference [1], however, this technology is significantly behind modulator integration in terms of the number of devices on a chip and the device yield as described in reference [2]. (In this specification, a reference is designated by a number in brackets to identify its location in a list of references found in the Appendix)
Therefore what is needed is an arrangement in which multiple optical transceivers can be integrated onto a single optoelectronic chip to accommodate large number of optical inputs and outputs at the switch unit.
In accordance with the method and apparatus of our invention, an optical communication network includes remote units which each provide an optical carrier signal which is used for signaling by a centralized optoelectronic switch. The remote units include a standard network interface card (NIC) with an optical transceiver which is slightly modified so that instead of being normally xe2x80x9coffxe2x80x9d during the standby mode, the data signal is logically inverted to be xe2x80x9con.xe2x80x9d The light from each NIC is used to provide optical carrier signal for a corresponding optical modulator at the switch unit. This eliminates the requirement for integrating vertical cavity surface emitting lasers (VCSELs) or light emitting diodes (LEDs) on an optoelectronic switch chip at the switch unit.
More particularly, in accordance with my invention, an optical communication network comprises a plurality of remote optical transceiver units connected over a plurality of optical fibers to an optoelectronic switch unit. Each remote optical transceiver unit includes an optical signal source for transmitting a modulated optical upstream signal to the optoelectronic switch during a transmit mode, and during a standby mode transmitting an optical carrier signal. The optoelectronic switch includes a plurality of local transceivers, each local transceiver operating as a receiver during the transmit mode to receive the upstream optical signal over an optical fiber from one of the plurality of remote optical transceiver units and operating as a modulator during the standby mode to modulate a received optical carrier signal and transmitting the modulated downstream optical signal back to that one of the plurality of remote optical transceiver units.
In accordance with one feature of the invention, each local transceiver includes a multiple quantum well (MQW) device which is switchable for use as a modulator and as a detector. According to another feature each MQW device is made part of a Very Large Scale Integrated (VLSI) circuit.